Field of the Invention
This application claims priority to Japanese Patent Application No. 2015-069525 filed on Mar. 30, 2015, the entire contents of which are incorporated by reference herein.
The present invention relates to an individual identification technique using biometric information, and more particularly to setting an identification threshold in individual identification using biometric information.
Description of the Related Art
Individual identification devices (individual authentication devices) have been heretofore used to determine whether or not an identification subject is a registrant by using biometric information such as a face, fingerprint, palm print, iris, or voice print. An individual identification device usually calculates a similarity between the biometric information on an identification subject and biometric information on a registrant, determines that the subject is the registrant when the similarity is equal to or higher than an identification threshold, and determines that the subject is not a registrant when the similarity is below the identification threshold.
In this case, where a large identification threshold is set, a false acceptance rate (FAR) of determining that a person who is not the registrant is the registrant can be suppressed, but a false rejection rate (FRR) of determining that the registrant is not the registrant increases. Conversely, where a small identification threshold is set, the false rejection rate can be suppressed, but the false acceptance rate increases. Therefore, determining adequately the identification threshold is important in terms of performing adequate biometric authentication.
Japanese Patent Application Publication No. 2004-46697 discloses a method in which biometric information on a non-registrant is also prepared in addition to biometric information on a registrant, the similarity of a subject and the non-registrant is calculated in addition to the similarity of the subject and the registrant, matching is performed, and an identification threshold is determined using the identification result. Where biometric information on a non-registrant is thus used, the sample number is increased and the identification threshold is determined from a large number of samples. Therefore, the identification threshold obtained is more suitable than that determined on the basis of identification result relating only to the registrant.
Further, Japanese Patent Application Publication No. 2008-117271 discloses a face recognition device in which where the capture position or timing of a face image of a recognition subject is close to the capture position or timing of the face image subjected to recognition processing, a threshold is lowered. Otherwise, the threshold is raised. In Japanese Patent Application Publication No. 2008-117271, when the capture positions or timings of face image are close, it is highly probable that an individual included in the face image is the same. Therefore, accurate recognition can be performed even when a low similarity is calculated due to the face orientation or illumination conditions.